Heating and Cooling Seasons
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STEM
Heating and Cooling Seasons
Have you watched weather reports to decide what to wear or what outdoor
activities to schedule? Have you watched a weather report to learn what weather
conditions are predicted for the next few days? Some weather reports include
weather predictions for seven to ten days.
Climatologists study weather conditions for much longer time periods. One
way that climatologists study weather is to analyze two different 12 month
periods called cooling seasons and heating seasons.
Cooling Seasons
A cooling season is a 12 month season that begins January 1 st each
year and ends on December 31st so that the warmer months are in the middle of
the cooling season. Cooling seasons are used to analyze how much a cooling
system is needed to keep a building cool during warm weather.
Heating Seasons
A heating season is a 12 month season that starts in July 1st of one year and
ends on June 30th of the next year so that colder months are in the middle of the
heating season. Heating seasons are used to analyze how much a heating
system is needed to keep a building warm during cold weather.
Cooling and Heating Degree Day Calculations
Climatologists make a calculation called a degree day during cooling seasons
and heating seasons.
1. First, climatologists determine the average temperature for a day.
2. The following formula determines if cooling degree days heating degree
days have accumulated during a 24 hour period.
Degree days = One day x (65º - average temperature for the day)
Question 1: Why would a negative value for the number of degree days mean
that a cooling system might be needed for a building?
Question 2: Why would a positive value for the number of degree days mean
that a heating system might be needed for a building?
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A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by
the Climate System Research Center in conjunction with the International Polar Year
Heating and Cooling Seasons
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A Sample Cooling Degree Day Calculation
A day’s high temperature was 87º F.
A day’s high temperature was 63º F.
The number of degree days = # of days x (65º - average temp.)
The number of degree days = 1 day x (65º - 75º)
The number of degree days = − 10
Notice the negative value for the number of degree day. That is because the
daily average temperature was above 65º F. As a result a cooling system may
have been use in buildings. Therefore, 10 cooling degree days accumulated on
that day. That would mean that 10 units of energy would be needed to operate a
cooling system on that day.
A Sample Heating Degree Day Calculation
A day’s high temperature was 47º F.
A day’s low temperature was 23º F.
The number of degree days = # of days x (65º - average temp.)
The number of degree days = 1 day x (65º - 35º)
The number of degree days = 30
Notice the positive value for the number of degree day. That is because the
daily average temperature was below 65º F. As a result a heating system may
have been use in buildings. Therefore, 30 heating degree days accumulated on
that day. That would mean that 30 units of energy would be needed to operate a
heating system on that day.
Calculate Heating or Cooling Degree Days
During some months of a cooling season there are some days when the
average temperature is above 65º F. There are also some days when the
average temperature is below 65º F.
Question 4: The high temperature for a day in September was 89º F and the
low temperature was 72º F. How many degree days accumulated on that day
and were they cooling degree days or heating degree days?
Question 5: The high temperature for a day in September was 79º F and the
low temperature was 62º F. How many degree days accumulated on that day
and were they cooling degree days or heating degree days?
Question 6: The high temperature for a day in September was 69º F and the
low temperature was 52º F. How many degree days accumulated on that day
and were they cooling degree days or heating degree days?
Heating and Cooling Seasons
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Degree Days Accumulate
When daily average temperatures fluctuate above and below 65º F, the
degree day formula must be used on a daily basis to accurately calculate the
number of heating and cooling degree days that accumulate.
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When the degree day formula results in a positive value, the number
of degree days is referred to as heating degree days because the
average outside temperature was below 65º F.
When the degree day formula results in a negative value, the number
of degree days is referred to as cooling degree days because the
average outside temperature was above 65º F.
The following table includes data that can be used to monitor the number of
heating degree days (HDD) and cooling degree days (CDD) that accumulate
during a week.
1. Calculate the average temperature for each day in the data table.
2. Then use the degree day formula to calculate either the number of cooling
degree days or the number of heating degree days that accumulate each
day.
3. Record the number of degree days accumulated each day in the
appropriate column.
Day
High
Low
Average
Temperature Temperature Temperature
Monday
75º F
63º F
Tuesday
77º F
69º F
Wednesday
81º F
69º F
Thursday
70º F
62º F
Friday
68º F
62º F
Saturday
60º F
58º F
Sunday
55º F
42º F
HDD
CDD
Question 7: How many cooling degree days accumulate during the week?
Question 8: How many heating degree days accumulate during the week?
Heating and Cooling Seasons
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Explore Cooling and Heating Season
You also have been given maps of the United States published by The
National Climate Data Center. The maps indicate the total number of degree
days that accumulate during an entire cooling season and an entire heating
season.
Three forms of the Cooling Degree Day and Heating Degree Day maps are
available at:
http://lwf.ncdc.noaa.gov/oa/documentlibrary/clim81supp3/clim81.html
The three map formats at the web site are:
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Low Resolution maps. In this format, the entire map of the United States is
enlarged slightly for viewing by clicking anywhere on the map.
High Resolution maps. In this format, one section of the map is magnified
so that a region of the United States can be studied in more detail.
Maps as ADOBE PDF files that can be saved on a computer.
Question 9: What is the total number of cooling degree days that accumulate in
your region during an entire cooling season?
Question 10: What is the total number of heating degree days that accumulate in
your region during an entire heating season?
Question 11: How do a heating season in your region compare with a heating
season in the northern regions of Alaska that are above the Arctic Circle?
Question 12: What factors seem to influence the number of heating degree days
that accumulate in a region during a heating season?
Question 13: What factors seem to influence the number of cooling degree days
that accumulate in a region during a cooling season?
Question 14: Why do some states have a wide range of heating or cooling
seasons?
Question 15: Why do some states have a narrow range of heating or cooling
seasons?